Kevin ate 5 slices of cake. Christopher ate 4 slices. If there were initially 10 slices, what fraction of the cake was eaten?
Answer: $\text{fraction of cake eaten} = \dfrac{\text{number of slices eaten}}{\text{number of slices total}}$ They ate ${9}$ out of $10$ slices. They ate $\dfrac{9}{10}$ of the cake.